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Disjùnkt distribyuçion
隔離分佈（disjunct distribution），亦作'不連續分佈'（discontinuous distribution），是一個生物地理学的名詞，指某一分類單元因為地理上的隔絕而被分為兩組或更多相關的 地域。 隔離分佈的成因不儘相同：可能表明物種範圍的擴大或收縮，使本來相連的分佈地域被隔開 。 Range fragmentation Also called range fragmentation, disjunct distributions may be caused by changes in the environment, such as 造山運動 and 大陆漂移学说 or rising 海平面s; it may also be due to an 生物 expanding its range into new areas, by such means as , or other animals transporting an organism to a new location (plant seeds consumed by birds and animals, can be moved to new locations during bird or animals migrations, and those seeds can be deposited in new locations in fecal matter). Other conditions that can produce disjunct distributions include: flooding, or changes in wind, stream, and current flows, plus others such as anthropogenic introduction of alien 外來物種 either accidentally or deliberately (agriculture and horticulture). Habitat fragmentation Disjunct distributions can occur when suitable 棲息地 is 棲息地零碎化, which produces fragmented populations, and when that fragmentation becomes so divergent that species movement between one suitable habitat to the next is disrupted, isolated population can be produced. Extinctions can cause disjunct distribution, especially in areas where only scattered areas are habitable by a species; for instance, island chains or specific elevations along a mountain range or areas along a coast or between bodies of water like streams, lakes and ponds. Examples There are many patterns of disjunct distributions at many scales: Irano-Turanian disjunction, Europe - East Asia, Europe-South Africa (e.g. genus 歐石楠), Mediterranean-Hoggart disjunction (genus 木犀榄属), etc. Lusitanian distribution This kind of disjunct distribution of a species, such that it occurs in 伊比利亚半岛 and in 爱尔兰岛, without any intermediate localities, is usually called "Lusitanian" (named after the Roman Province 琉息太尼亞, corresponding to modern day 葡萄牙). Examples of animal species with a Lusitanian distribution are: the Kerry slug and the 比利牛斯山 glass snail . Plant species with this kind of distribution include several 帚石楠 species (Calluna spp.) and the 草莓樹 (Arbutus unedo). The theory behind the name "Lusitanian" is now discredited; it posited that there was an ice-free land mass that served as a off of the south-west of Ireland during the 第四紀 (last) 冰期. In this refugium, relic fauna and flora from a previous ice-free period survived until the present warmer 冰段 period末次冰期 or to 第四纪冰河时期?-->. Although the theory is no longer accepted, the term Lusitanian is still used as a descriptive term for faunal elements such as the Kerry slug. Recently a better explanation of the occurrence of the Kerry slug and similar faunal elements in southwestern Ireland has been developed. This new theory is supported by two recent discoveries: the genetic similarity of much of to that of northern Spain, and the genetic similarity of much of Ireland’s human population to that of northern Spain. Mascheretti et al. (2003)Masheretti S., Rogatcheva M. B., Gündüz I., Fredga K. & Searle J. B. 2003. [https://archive.is/20120629172226/http://www.journals.royalsoc.ac.uk/content/3b9a0gx50hplrm2b/ How did pygmy shrews colonize Ireland? Clues from a phylogenetic analysis of mitochondrial cytochrome b sequences]. Proc. Roy. Soc. B 270: 1593-1599. examined the genotypes of 小鼩鼱, a small mammal, across its range in Europe. The Irish population showed close genetic affinity to a population from 安道尔 but not to that of 大不列顛島 or other places in Europe. The genetic structure of the population further showed that the entire Irish population of the Eurasian pygmy shrew had originated from a single 奠基者效应. The authors concluded that it had been introduced in the early (旧石器时代) or middle (中石器時代) 石器時代, by boat, probably from south-west Europe. This coincides with work on human populations, which foundHill E. W., Jobling M. A. & Bradley D. G. 2000. Y chromosome variation and Irish origins. Nature 404: 351.McEvoy B., Richards M., Forster P. & Bradley D. G. 2004. The longue durée of genetic ancestry: multiple genetic marker systems and Celtic origins on the Atlantic facade of Europe. Am. J. Hum. Genet. 75: 693-702. a strong 遗传学 similarity in make-up between populations in western Ireland and in northern Spain. This would be explained by a human migration from Spain to Ireland in the late Paleolithic or early 中石器時代. It seems increasingly likely that much of Ireland’s Lusitanian fauna is in reality an artefact of this era of human expansion in the early part of the Postglacial era. In other words, it seems likely that these species were introduced accidentally with trade items or goods brought by boat from Iberia. 參看 * * 异域物种形成 * Habitat * 棲息地零碎化 參考文獻 外部連結 Category:生物地理学 Category:生物学术语 Category:棲息地 Category:生态学术语